Mask blank, method for manufacturing transfer mask, and method for manufacturing semiconductor device

ABSTRACT

A mask blank, which is capable of being formed with high transfer accuracy when a hard mask film pattern is used as a mask, and even when the mask blank includes a chromium-based light shielding film. A light-semitransmissive film, a light shielding film, and a hard mask film are laminated in the stated order on a transparent substrate. The light-semitransmissive film contains silicon, and the hard mask film contains any one or both of silicon and tantalum. The light shielding film has a laminate structure of a lower layer and an upper layer, and contains chromium. The upper layer has a content of chromium of 65 at % or more, and a content of oxygen of less than 20 at %, and the lower layer has a content of chromium of less than 60 at %, and a content of oxygen of 20 at % or more.

This is a Divisional of application Ser. No. 15/300,376 filed Sep. 29,2016, claiming priority based on International Application No.PCT/JP2015/059855 filed Mar. 30, 2015, claiming priority based onJapanese Patent Application No. 2014-070686 filed Mar. 30, 2014, thecontents of all of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

This invention relates to a method of manufacturing a transfer mask usedin manufacturing a semiconductor device, and a mask blank used inmanufacturing the transfer mask.

BACKGROUND ART

In general, in a manufacturing step of a semiconductor device, a finepattern is formed using a photolithography method. Further, in formingthe fine pattern, a large number of transfer masks (also generallycalled photomasks) are generally used. In a transfer mask, in general, alight shielding blocking fine pattern formed of a metal thin film or thelike is provided on a transparent glass substrate. The photolithographymethod is also used in manufacturing this transfer mask.

The transfer mask is an original plate for transferring the same finepattern in high volume. Therefore, the dimensional accuracy of a patternformed on the transfer mask directly affects the dimensional accuracy ofthe fine pattern to be manufactured. As the degree of integration of asemiconductor circuit is improved, the dimensions of the pattern becomesmaller, and the accuracy of the transfer mask is required to be higher.

Hitherto, as such transfer mask, there have been well known a binarymask, in which a transfer pattern formed of a light shielding film isformed on a transparent substrate, e.g., a glass substrate, a phaseshift mask, in which a transfer pattern formed of a phase shift film, orof a phase shift film and a light shielding film is formed on thetransparent substrate, and other type of masks. There has also beenknown a halftone-type phase shift mask, in which a light shielding bandis formed in a peripheral portion of a transfer pattern forming region.

For example, in WO-A-2004/090635 (Patent Document 1), there isdescribed, as a mask blank for manufacturing a halftone-type transfermask, a mask blank having the thin-film structure including, from asubstrate side, a metal silicide-based transfer mask film(light-semitransmissive film), a light shielding film made of achromium-based compound, and a hard mask film made of a siliconcompound.

PRIOR ART DOCUMENTS Patent Document

Patent Document 1: WO-A-2004/090635

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

When such mask blank as described in Patent Document 1 is patterned,first, the hard mask film made of the silicon compound is patterned bydry etching using a fluorine-based gas, and using as a mask apredetermined resist pattern formed on a surface of the mask blank.Next, the light shielding film made of the chromium-based compound ispatterned by dry etching using a mixture gas of chlorine and oxygen, andusing the patterned hard mask film as a mask. Subsequently, a metalsilicide-based transfer mask film (light-semitransmissive film) ispatterned by dry etching using a fluorine-based gas, and using thepatterned light shielding film as a mask.

Meanwhile, when a proportion of a chromium element contained in acomposition is high, the above-mentioned chromium-based light shieldingfilm has a high extinction coefficient, and hence is advantageous inthat high optical density is obtained even when a film thickness isreduced. However, when the proportion of the chromium element becomeshigher, an etching rate becomes lower, and more time is required for thepatterning. Therefore, there is a fear that the pattern of the hard maskfilm, which is above the light shielding film, may disappear before thepatterning of the light shielding film is complete.

Moreover, when the light shielding film is patterned by the dry etching,at a stage in which an etching gas reaches a lower surface of the lightshielding film, a surface side of the light shielding film hassubstantially the same space width as that of the pattern of the hardmask film, and in contrast, etching in side wall sides of the lowersurface does not proceed sufficiently, with the result that the lowersurface has a space width that is smaller than that of the pattern ofthe hard mask film, and that a cross-sectional shape of the side wallshas a portion that is in an inclined state. Therefore, there is a needto perform additional etching (over etching) so that the spaces of thelight shielding film pattern are formed reliably also in the lowersurface.

However, when a proportion of chromium element contained in thecomposition of the chromium-based light shielding film is large, theetching rate is low. Therefore, in order to reliably form the spaces inthe lower surface, there arises a need to perform the over etching for along period of time. However, when the over etching is performed for thelong period of time, a surface of a metal silicide-based transfer maskfilm, which is a layer below the light shielding film, is damaged, andhence there is a problem in that the over etching cannot be performedvery long.

To the contrary, when the proportion of the chromium element containedin the composition is low, the etching rate becomes higher, but theextinction coefficient becomes lower. Therefore, in order to obtainpredetermined optical density, the film thickness needs to be increased.Moreover, a film having the small proportion of chromium element has afilm stress that exhibits a tendency toward compressive stress, andhence when a film thickness is increased to obtain the optical density,there is a fear that a front surface of the mask blank may be deformedunder the effect of the compressive stress. The deformation of thesurface of the mask blank affects positional accuracy during patternformation.

Moreover, the mixture gas of chlorine and oxygen, which is used in thedry etching of the chromium-based light shielding film, has a propertyof isotropic etching. Therefore, when the etching rate is high becausethe chromium component is small, and the film thickness is thick, sidewalls of the pattern are also eroded by the etching gas. As a result,the light shielding film pattern becomes thinner than that of the hardmask film pattern, which is above the light shielding film pattern, andpattern accuracy of the transfer mask film, which is formed by thepatterning using the light shielding film pattern as the mask, isdeteriorated.

As a countermeasure, there is known a method in which the resist patternis formed to have large dimensions at line portions thereof and smalldimensions at space portions thereof in consideration of thinning of thelight shielding film pattern. However, when the width dimension of thespaces of the resist pattern is small, there is also a problem in thatdevelopment for the formation of the spaces becomes more difficult.

This invention has been made in view of the above-mentioned problems inthe relate art, and therefore has the following objects: firstly, toprovide a mask blank, which is capable of being formed with hightransfer accuracy when a hard mask film pattern is used as a mask, andeven when the mask blank includes a chromium-based light shielding film;secondly, to provide a method of manufacturing a transfer mask in whichthe fine pattern is formed with high accuracy using such mask blank; andthirdly, to provide a method of manufacturing a high-qualitysemiconductor device with excellent pattern accuracy using such transfermask.

Means to Solve the Problem

The inventors of this invention have devised this invention based onfindings obtained as a result of conducting, on a mask blank having thestructure in which a light-semitransmissive film, a light shieldingfilm, and a hard mask film are laminated in the stated order on atransparent substrate, intense research in which the above-mentionedlight shielding film has a predetermined laminated structure, focusingattention on side etching amounts in dry etching using a mixture gas ofa chlorine gas and an oxygen gas in respective layers of the lightshielding film.

Specifically, in order to solve the problems described above, thisinvention has the following configuration.

(Configuration 1)

A mask blank having a structure in which a light-semitransmissive film,a light shielding film, and a hard mask film are laminated in the statedorder on a transparent substrate, the light-semitransmissive film atleast containing silicon, the hard mask film being formed in contactwith a surface of the light shielding film, and at least containing anyone or both of silicon and tantalum, the light shielding film having alaminated structure of a lower layer and an upper layer, and at leastcontaining chromium, the upper layer having a content of the chromium of65 at % or more, and a content of oxygen of less than 20 at %, the lowerlayer having a content of the chromium of less than 60 at %, and acontent of oxygen of 20 at % or more.

According to Configuration 1, the upper layer of the light shieldingfilm containing chromium, which is immediately below the hard mask film,has a high content of chromium (is chromium-rich) and a low content ofoxygen, with the result that the etching rate is low, and side etchingduring the etching is less likely to occur (side walls of the patternare less likely to be eroded). With the side etching in the upper layerof the light shielding film being less likely to occur, a pattern shapeof the hard mask film, which is immediately above the upper layer of thelight shielding film, is transferred substantially accurately to theupper layer. With the light shielding film including the upper layer, towhich the pattern shape of the hard mask film has been transferredsubstantially accurately, the pattern of the hard mask film can also beformed substantially accurately in the light-semitransmissive filmcontaining silicon, which is patterned by a fluorine-based gas being ananisotropic etching gas using the pattern of the light shielding film asthe mask.

Moreover, according to Configuration 1, there are also obtained effectsof reducing the film stresses of thin films formed into the mask blank,and of suppressing the deformation of the surface of the mask blank.

A silicon-based compound adopted for the light-semitransmissive film inConfiguration 1 is less susceptible to damages of the films due toheating processing and the like, and hence processing of heating up to300° C. or more can be performed. A metal silicide-based thin filmformed by the sputtering can reduce a film stress to a negligible degreeby the above-mentioned heating processing. Meanwhile, a chromium-basedthin film is significantly changed in film quality when high-temperatureprocessing is performed after the film formation, and hence is notpositively subjected to the high-temperature processing. Therefore, thechromium-based thin film is difficult to reduce the film stress by posttreatment such as heat treatment after sputter deposition. Further, whena hard mask film made of a silicon-based thin film or a tantalum-basedthin film is formed after the chromium thin film is formed, thesilicon-based thin film or the tantalum-based thin film cannot be heatedafter the formation, and hence it is difficult to reduce film stressesthereof.

The film stress of the chromium-based thin film exhibits a tendencytoward weak compressive stress when the proportion of chromium elementis small. As the proportion of chromium element becomes larger, thecompressive stress becomes gradually weaker. Further, the film stressexhibits a tendency toward strong tensile stress when the proportion ofchromium element is increased. Configuration 1 relates to a mask blankin which an upper layer, which has a large proportion of chromiumelement and hence a stress tendency that is a tendency toward tensilestress, is formed on a lower layer, which has a small proportion ofchromium element and hence a tendency toward compressive stress.Therefore, according to Configuration 1, the chromium-based thin film,which has the small proportion of chromium element having the tendencytoward compressive stress, can be reduced in thickness, and henceimbalance in total film stress of the light shielding film can bereduced. Further, the silicon-based thin film exhibits a compressivestress without annealing. Therefore, a layer having a large proportionof chromium element, which imparts a tendency toward tensile stress, canbe included in the light shielding film to reduce the total film stressof the thin films formed on the substrate. As a result, the deformationof the surface of the mask blank can also be effectively suppressed, anda pattern having an excellent positional accuracy can be formed.

Moreover, the lower layer of the light shielding film has a content ofchromium that is lower than that of the upper layer, and a content ofoxygen that is higher than that of the upper layer. As a result, thereis adopted a film design in which the lower layer has a high etchingrate, and hence the etching rate of the light shielding film as a wholecan be increased. Consequently, the patterning of the light shieldingfilm can be completed without a disappearance of the pattern in the hardmask film.

As described above, according to Configuration 1, even such finetransfer pattern can be formed in the light-semitransmissive film, whichfunctions as the transfer mask film of the mask blank according to thisinvention, with high accuracy, and as a result, the transfer mask withexcellent pattern accuracy can be manufactured.

(Configuration 2)

The mask blank according to Configuration 1, wherein the lower layer hasa content of the chromium of 40 at % or more.

According to Configuration 1, the content of chromium in the lower layerof the light shielding film is less than 60 at %. However, when thecontent of chromium is too low, an extinction coefficient k with respectto, for example, an ArF excimer laser light (wavelength: 193 nm) is low,and hence there arises a need to increase the film thickness of thelight shielding film (especially the lower layer) to obtain thepredetermined optical density. To address this problem, as inConfiguration 2, the content of chromium in the lower layer is set to 40at % or more such that the above-mentioned extinction coefficient k isincreased. As a result, the light shielding film can be reduced inthickness, and accuracy of patterning the light-semitransmissive filmusing the pattern of the light shielding film as the mask can beincreased.

(Configuration 3)

The mask blank according to Configuration 1 or 2, wherein the lowerlayer has a content of the oxygen of 30 at % or less.

According to Configuration 1, the lower layer of the light shieldingfilm has the content of oxygen of 20 at % or more, but it is preferredthat the lower layer have the content of oxygen of 30 at % or less as inConfiguration 3. When the content of oxygen of the lower layer becomeshigher than 30 at %, the etching rate of the lower layer is increased,but progress of side etching in the lower layer portion is alsoincreased in speed, with the result that a clear step may be formed at aboundary between the upper layer and the lower layer in the crosssection of the pattern. With such step, when a finer pattern is to beformed, there is a fear that the light shielding film pattern may fall.

As in this Configuration, when the content of oxygen of the lower layeris in the above-mentioned range, the etching rate of the lower layer iskept high. As a result, the etching rate of the entire light shieldingfilm can also be kept high, and the effect of the side etching in thelower layer portion can be suppressed.

Moreover, when the content of oxygen contained in the lower layer is inthe above-mentioned range, there can also be obtained the effect offurther enhancing adhesion between the light shielding film pattern andthe light-semitransmissive film. This is because, at an interfacebetween the light shielding film and the light-semitransmissive film,oxygen elements are moved and connected by chemical bonds.

(Configuration 4)

The mask blank according to any one of Configurations 1 to 3, whereinthe lower layer is dry-etched using a mixture gas of a chlorine gas andan oxygen gas at an etching rate that is three times an etching rate atwhich the upper layer is dry-etched using the mixture gas of thechlorine gas and the oxygen gas or more.

As in Configuration 4, with the lower layer of the light shielding filmbeing dry-etched using the mixture gas of the chlorine gas and theoxygen gas at the etching rate that is three times the etching rate ofthe upper layer or more, the etching rate in the depth direction isincreased when the etching proceeds from the upper layer to the lowerlayer, and the etching in the depth direction of the lower layer can becompleted while suppressing the progress of the side etching in theupper layer.

(Configuration 5)

The mask blank according to any one of Configurations 1 to 4, whereinthe lower layer has a structure in which a bottom layer and anintermediate layer are laminated in the stated order from thelight-semitransmissive film side.

As in Configuration 5, with the lower layer having the structure inwhich the bottom layer and the intermediate layer are laminated in thestated order from the light-semitransmissive film side, the intermediatelayer is formed between the upper layer and the bottom layer of thelight shielding film so that the light shielding film has thethree-layer structure. As a result, the contents of chromium in therespective layers can be adjusted to control, for example, the etchingrate of the light shielding film in three stages to thereby suppress theformation of the step due to the difference in degree of progress of theside etching in the side walls of the pattern of the light shieldingfilm, and to thereby improve the cross-sectional shape of the pattern ofthe light shielding film as compared to the light shielding film havingthe two-layer structure.

(Configuration 6)

The mask blank according to Configuration 5, wherein the bottom layer isdry-etched using a mixture gas of a chlorine gas and an oxygen gas at anetching rate that is three times an etching rate at which the upperlayer is dry-etched using the mixture gas of the chlorine gas and theoxygen gas or more.

As in Configuration 6, with the bottom layer of the light shielding filmhaving the three-layer laminated structure being dry-etched using themixture gas of the chlorine gas and the oxygen gas at the etching ratethat is three times the etching rate of the upper layer or more, theside wall portion of the pattern in the upper layer is hardly etchedduring the etching of the bottom layer, and the etching in the depthdirection of the bottom layer can be completed while suppressing theprogress of the side etching of the upper layer.

(Configuration 7)

The mask blank according to Configuration 5 or 6, wherein the bottomlayer is dry-etched using a mixture gas of a chlorine gas and an oxygengas at an etching rate that is higher than and two times an etching rateat which the intermediate layer is dry-etched using the mixture gas ofthe chlorine gas and the oxygen gas or less.

In a case where an etching rate in the bottom layer is relatively higherthan that in the intermediate layer, when the etching proceeds from theintermediate layer to the bottom layer, the etching rate in the depthdirection is increased. As in Configuration 7, with the etching rate ofthe bottom layer being two times the etching rate of the intermediatelayer or less in the etching in the bottom layer and over etchingnecessary for reliably forming a space portion of the pattern arecompleted during the etching of the bottom layer before the side etchingproceeds more in the intermediate layer, and hence formation of a stepcan be suppressed especially at the interface of the side walls of thepattern between the intermediate layer and the bottom layer.

Moreover, it is preferred that the etching rate of the bottom layer behigh because the time for over etching can be reduced. Meanwhile, whenthe etching rate of the bottom layer is too high, the side wall portionof the pattern is deeply eroded by the etching gas in the bottom layerportion, and there is a risk of reducing a contact area between thelight-semitransmissive film and the light shielding film pattern. Whenthe etching rate of the bottom layer is in the above-mentioned range,the erosion of the side walls of the pattern in the bottom layer canalso be suppressed while reducing the time for over etching.

(Configuration 8)

The mask blank according to any one of Configurations 1 to 7, whereinthe upper layer has a thickness of 1.5 nm or more and 8 nm or less.

As in Configuration 8, with the upper layer of the light shielding filmhaving the thickness in a range of 1.5 nm or more and 8 nm or less, thegood patterning accuracy for the upper layer can be maintained whilesatisfactorily suppressing the etching time of the upper layer. Apreferred thickness of the upper layer is 3 nm or more and 8 nm or less.

(Configuration 9)

The mask blank according to any one of Configurations 1 to 8, whereinthe light shielding film has a thickness of 35 nm or more and 55 nm orless.

As in Configuration 9, with the light shielding film having thethickness of 35 nm or more and 55 nm or less, the thickness of theentire light shielding film can be reduced, and the accuracy ofpatterning the light-semitransmissive film using the pattern of thelight shielding film as the mask can be increased.

(Configuration 10)

The mask blank according to any one of Configurations 1 to 9, whereinthe hard mask film contains oxygen.

The hard mask film needs to be made of a material having high etchingselectivity with respect to the light shielding film, which isimmediately below the hard mask film. As in Configuration 10, a materialcontaining an oxide in addition to silicon or tantalum can be selectedfor the hard mask film to secure the high etching selectivity withrespect to the light shielding film, which is made of a chromium-basedmaterial, and not only a resist but also the hard mask film can bereduced in thickness. Therefore, accuracy of transferring the resistpattern formed in the surface of the mask blank is improved, therebybeing capable of forming a pattern with excellent pattern accuracy inthe light shielding film.

(Configuration 11)

The mask blank according to any one of Configurations 1 to 10, whereinthe light-semitransmissive film contains silicon and nitrogen.

As in Configuration 11, a material containing silicon and nitrogen canbe applied to the light-semitransmissive film to secure etchingselectivity with respect to the light shielding film, which is made ofthe chromium-based material. Moreover, when the material containingsilicon and nitrogen is used, patterning using an anisotropicfluorine-based gas as an etching gas can be applied. Therefore, thelight shielding film pattern, to which the pattern shape of the hardmask film has been transferred substantially accurately, can be used asthe mask to also form a pattern having excellent pattern accuracy in thelight-semitransmissive film.

(Configuration 12)

The mask blank according to any one of Configurations 1 to 11, whereinthe light-semitransmissive film and the light shielding film form alaminated structure having a transmittance of 0.2% or less with respectto an ArF excimer laser light (wavelength: 193 nm).

As in Configuration 12, the laminated structure of thelight-semitransmissive film and the light shielding film has atransmittance of 0.2% or less with respect to the ArF excimer laserlight (wavelength: 193 nm). Thus, the laminated structure can have goodlight shielding property (optical density of 2.7 or more) with respectto the ArF excimer laser light as the exposure light in a preferredmanner.

(Configuration 13)

The mask blank according to any one of Configurations 1 to 12, whereinthe light-semitransmissive film and the light shielding film form alaminated structure having a transmittance of 50% or less with respectto light having a wavelength in at least a part of a wavelength regionof from 800 nm to 900 nm.

The resist is not sensitive to light in a near-infrared region having awavelength of from 800 nm to 900 nm, and hence the light is used foralignment when the mask blank is placed in an exposure apparatus. As inConfiguration 13, the laminated structure of the light-semitransmissivefilm and the light shielding film has a transmittance of 50% or lesswith respect to light having a wavelength in at least a part of thewavelength region of from 800 nm to 900 nm. Thus, the laminatedstructure enables easy placement of the mask blank in the exposureapparatus in a preferred manner.

(Configuration 14)

The mask blank according to any one of Configurations 1 to 13, whereinthe hard mask film and the light-semitransmissive film are patterned bydry etching using a fluorine-based gas.

According to Configuration 14, the hard mask film and thelight-semitransmissive film are patterned by the dry etching using theanisotropic fluorine-based gas. Consequently, together with thesubstantially accurate transfer of the pattern shape of the hard maskfilm, which is immediately above the upper layer of the light shieldingfilm, to the upper layer, the transfer pattern can be formed withexcellent form accuracy of the pattern in the light-semitransmissivefilm by the patterning using the light shielding film as the mask.

(Configuration 15)

A method of manufacturing a transfer mask using the mask blank of anyone of Configurations 1 to 14, the method comprising the steps of:forming a light-semitransmissive film pattern in the hard mask film bydry etching using a fluorine-based gas and using as a mask a resistfilm, which is formed on the hard mask film and has thelight-semitransmissive film pattern; forming the light-semitransmissivefilm pattern in the light shielding film by dry etching using a mixturegas of a chlorine gas and an oxygen gas, and using as a mask the hardmask film, in which the light-semitransmissive film pattern has beenformed; forming the light-semitransmissive film pattern in thelight-semitransmissive film by dry etching using a fluorine-based gasand using as a mask the light shielding film, in which thelight-semitransmissive film pattern has been formed; and forming a lightshielding pattern in the light shielding film by dry etching using amixture gas of a chlorine gas and an oxygen gas, and using as a mask aresist film, which is formed on the light shielding film and has a lightshielding pattern.

As in Configuration 15, the transfer mask can be manufactured followingthe above-mentioned manufacturing steps and using the mask blankaccording to this invention to obtain the transfer mask in which a finepattern being, for example, less than 80 nm is formed with highaccuracy.

(Configuration 16)

A method of manufacturing a semiconductor device, comprising a step ofpatterning and transferring a transfer pattern of a transfer mask, whichis manufactured by the method of manufacturing a transfer mask ofConfiguration 15, on a semiconductor substrate by a lithography methodusing the transfer mask.

As in Configuration 16, a high-quality semiconductor device can beobtained with excellent pattern accuracy using the transfer mask inwhich the above-mentioned fine pattern is formed with high accuracy.

Effect of the Invention

According to the mask blank of this invention, even the fine transferpattern can be formed with high accuracy. More specifically, accordingto the mask blank of this invention, the upper layer of the lightshielding film has the high content of chromium (is chromium-rich) andthe low content of oxygen, and hence has the low etching rate, with theresult that the upper layer pattern is less susceptible to the sideetching. Therefore, there can be formed the light shielding film patternto which the shape of the transfer pattern, which is formed in theresist film or the hard mask film, is transferred substantiallyaccurately. As a result, when the light-semitransmissive film ispatterned using the light shielding film pattern as the mask, thetransfer pattern having the excellent pattern accuracy can be formed inthe light-semitransmissive film. Moreover, the lower layer of the lightshielding film has the high etching rate, and hence can increase theetching rate of the entire light shielding film, with the result thatthe formation of the light shielding film pattern can be completedreliably before the hard mask film pattern disappears.

Moreover, the transfer mask in which the fine pattern is formed withhigh accuracy can be manufactured using the above-mentioned mask blankaccording to this invention.

Further, the high-quality semiconductor device having the excellentpattern accuracy can be manufactured using the above-mentioned transfermask.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic cross-sectional view of a mask blank according toa first embodiment of this invention.

FIG. 2 is a schematic cross-sectional view of a mask blank according toa second embodiment of this invention.

FIG. 3A is a schematic cross-sectional view of the mask blank and thelike, for illustrating a manufacturing step of a transfer mask using themask blank according to this invention.

FIG. 3B is a schematic cross-sectional view of the mask blank and thelike, for illustrating a manufacturing step of the transfer mask usingthe mask blank according to this invention.

FIG. 3C is a schematic cross-sectional view of the mask blank and thelike, for illustrating a manufacturing step of the transfer mask usingthe mask blank according to this invention.

FIG. 3D is a schematic cross-sectional view of the mask blank and thelike, for illustrating a manufacturing step of the transfer mask usingthe mask blank according to this invention.

FIG. 3E is a schematic cross-sectional view of the mask blank and thelike, for illustrating a manufacturing step of the transfer mask usingthe mask blank according to this invention.

FIG. 4 is a cross-sectional view for illustrating a cross-sectionalshape of a light shielding film pattern in Example 1 of this invention.

FIG. 5 is a cross-sectional view for illustrating a cross-sectionalshape of a light shielding film pattern in Example 2 of this invention.

FIG. 6 is a cross-sectional view for illustrating a cross-sectionalshape of a light shielding film pattern in Comparative Example of thisinvention.

MODES FOR EMBODYING THE INVENTION

Now, embodiments of this invention will be described in detail withreference to the drawings.

As described above, as a result of conducting, on a mask blank havingthe structure in which a light-semitransmissive film, a light shieldingfilm, and a hard mask film are laminated in the stated order on atransparent substrate, intense research in which the light shieldingfilm has the predetermined laminated structure, focusing attention onside etching amounts in dry etching using a mixture gas of a chlorinegas and an oxygen gas in the respective layers of the light shieldingfilm, the inventors of this invention have found that theabove-mentioned problems can be solved by this invention having thefollowing configurations.

That is, as Configuration 1 described above, this invention is a maskblank having a structure in which a light-semitransmissive film, a lightshielding film, and a hard mask film are laminated in the stated orderon a transparent substrate, the light-semitransmissive film at leastcontaining silicon, the hard mask film being formed in contact with asurface of the light shielding film, and at least containing any one orboth of silicon and tantalum, the light shielding film having alaminated structure of a lower layer and an upper layer, and at leastcontaining chromium, the upper layer having a content of the chromium of65 at % or more, and a content of oxygen of less than 20 at %, the lowerlayer having a content of the chromium of less than 60 at %, and acontent of oxygen of 20 at % or more.

FIG. 1 is a schematic cross-sectional view of a mask blank according toa first embodiment of this invention.

As illustrated in FIG. 1, a mask blank 10 according to a firstembodiment of this invention has the structure in which alight-semitransmissive film 2, a light shielding film 3, and a hard maskfilm 4 are laminated in the stated order on a transparent substrate 1.Moreover, the light shielding film 3 has a laminated structure of alower layer 31 and an upper layer 33.

In the mask blank 10, the light-semitransmissive film 2 at leastcontains silicon, and the hard mask film 4 contains any one or both ofsilicon and tantalum. Moreover, the light shielding film 3 having thelaminated structure at least contains chromium. Note that, althoughdetails are to be described below, it is particularly preferred to applya material containing silicon and nitrogen to the light-semitransmissivefilm 2, and it is particularly preferred to apply a material containingoxygen in addition to silicon or tantalum to the hard mask film 4.

Here, the transparent substrate 1 in the mask blank 10 is notparticularly limited as long as being a substrate used in a transfermask for manufacturing a semiconductor device. When used in a blank fora phase shift type mask, the transparent substrate is not particularlylimited as long as being a substrate having transparency with respect toan exposure wavelength to be used, and a synthetic quartz substrate andother such glass substrates (for example, soda-lime glass,aluminosilicate glass, and other type of glass) are used. Among others,the synthetic quartz substrate has high transparency in a region of ArFexcimer laser (wavelength: 193 nm) or lower wavelength, which iseffective in forming a fine pattern, and hence is used particularlypreferably.

A material containing silicon (Si) or a material containing tantalum(Ta) can be used as such hard mask film 4. An example of the materialcontaining silicon (Si), which is suitable for the hard mask film 4, isa material containing silicon (Si) and one or more elements selectedfrom oxygen (O), nitrogen (N), carbon (C), boron (B), and hydrogen (H).Another example of the material containing silicon (Si), which issuitable for the hard mask film 4, is a material containing silicon(Si), a transition metal, and one or more elements selected from oxygen(O), nitrogen (N), carbon (C), boron (B), and hydrogen (H). In addition,examples of the transition metal include molybdenum (Mo), tungsten (W),titanium (Ti), tantalum (Ta), zirconium (Zr), hafnium (Hf), niobium(Nb), vanadium (V), cobalt (Co), chromium (Cr), nickel (Ni), ruthenium(Ru), and tin (Sn).

When a thin film containing oxygen (O) in addition to silicon (Si) isformed by a sputtering method, the thin film has a tendency towardcompressive stress. In order to reduce the stress, it is effective toperform heat treatment (annealing) as a post treatment after the filmformation. However, in this embodiment, the thin film is formed on thesurface of the light shielding film 3 made of the chromium-basedmaterial, and hence heat treatment at 300° C. or more, for example,cannot be performed. This is because there is a fear that the lightshielding film 3 made of the chromium-based material may be damaged bythe heat treatment.

The tendency toward compressive stress is relatively strong, and, forexample, when a 1.5 nm SiON film is directly formed on a surface of asynthetic quartz glass substrate (152 mm by 152 mm, thickness: 6 mm) fora mask blank by reactive sputtering, the SiON film has such tensilestress as to deform a shape of a surface of the substrate into a convexshape with a deformation amount of about 30 nm. The hard mask film 4 hasa thickness of at least 1.5 nm, and hence as the thickness becomeslarger, the deformation amount becomes larger.

Meanwhile, a chromium-based thin film exhibits a tendency towardcompressive stress when the proportion of chromium element is small, butexhibits a tendency toward stronger tensile stress as the proportion ofchromium element becomes higher. In this embodiment, the light shieldingfilm 3 has the structure in which the lower layer 31, which has a lowratio of chromium element, and the upper layer 33, which has a highratio of chromium element, are laminated. The upper layer 33 having thehigh ratio of chromium element has the tendency toward strong tensilestress, and hence the total film stress of the light shielding filmexhibits the tendency toward tensile stress. For example, when the lightshielding film 3 having a film configuration in which a film thicknessof the upper layer 31, which has the large tensile stress, is thesmallest, and in which a film thickness of the lower layer, which hasthe compressive stress, is the largest, and having a total filmthickness of 55 nm is directly formed on a synthetic quartz glasssubstrate (152 mm by 152 mm, thickness: 6 mm) for a mask blank, thelight shielding film 3 has such tensile stress as to deform a shape of asurface of the substrate into a concave shape with a deformation amountof 30 nm in depth. A total stress is varied depending on respectiveproportions of chromium element and respective film thicknesses, butwhen this embodiment is adopted, the light shielding film 3 has atensile stress with at least a deformation amount on the above-mentionedorder. When the upper layer 31 is increased in thickness and the lowerlayer 33 is reduced in thickness for the purpose of preventing the sideetching, the light shielding film 3 has an even stronger tendency towardtensile stress, and the deformation amount is increased.

In this embodiment, when the silicon (Si)-based material is used for thehard mask film 4, the film configuration, composition, film thickness,and the like of each of the hard mask film 4 and the light shieldingfilm 3 may be adjusted to cancel the respective stresses between thehard mask film 4 and the light shielding film 3. As a result, the totalfilm stress of the thin films on the mask blank may be minimized. Inother words, when the hard mask film 4 made of the silicon (Si)-basedmaterial is applied, there may be obtained a mask blank having a flattersurface shape. With the use of the mask blank having such surface shape,a pattern having excellent positional accuracy may be formed.

Meanwhile, an example of the material containing tantalum (Ta), which issuitable for hard mask film 4, is a material containing tantalum (Ta)and one or more elements selected from oxygen (O), nitrogen (N), carbon(C), boron (B), and hydrogen (H). Of those, a material containingtantalum (Ta) and oxygen (O) is particularly preferred. Specificexamples of such material include tantalum oxide (TaO), tantalumoxynitride (TaON), tantalum borate (TaBO), and tantalum boron oxynitride(TaBON).

Such hard mask film 4 has sufficient etching selectivity with respect tothe light shielding film 3, which is formed of a material containingchromium (Cr), and the hard mask film 4 may be removed by etching whilehardly damaging the light shielding film 3.

The film thickness of the hard mask film 4 does not need to beparticularly restricted, but is required to have at least such filmthickness as not to disappear before the etching of the light shieldingfilm 3, which is immediately below the hard mask film 4, is complete.Meanwhile, when the film thickness of the hard mask film 4 is thick, itis difficult to reduce the thickness of the resist pattern, which isimmediately above the hard mask film 4. From such viewpoints, in thisembodiment, the film thickness of the hard mask film 4 is preferably ina range of 1.5 nm or more and 20 nm or less, and particularly preferably2.5 nm or more and 6 nm or less.

The light-semitransmissive film 2 is formed of a material at leastcontaining silicon, but a configuration of the light-semitransmissivefilm 2 that is applicable to this invention does not need to beparticularly limited, and there may be applied a configuration of alight-semitransmissive film of a phase shift type mask that has hithertobeen used, for example.

Preferred examples of such light-semitransmissive film 2 include, forexample, a metal silicide-based light-semitransmissive film made of atransition metal and silicon, a metal silicide-basedlight-semitransmissive film made of a transition metal, silicon, and amaterial containing one or more elements selected from oxygen, nitrogen,and carbon, and a silicon-based light-semitransmissive film made ofsilicon and a material containing oxygen, nitrogen, carbon, boron, andthe like. Examples of the transition metal contained in theabove-mentioned metal silicide-based light-semitransmissive film includemolybdenum, tantalum, tungsten, titanium, chromium, nickel, vanadium,zirconium, ruthenium, and rhodium. Of those, molybdenum is particularlysuitable.

As the above-mentioned material containing a transition metal andsilicon, specifically, a transition metal silicide, or a materialcontaining a nitride, oxide, carbide, oxynitride, carbonate, or carbonoxynitride of a transition metal silicide is suitable. In addition, asthe above-mentioned material containing silicon, specifically, amaterial containing a nitride, oxide, carbide, oxynitride (oxidenitride), carbonate (carbide oxide), or carbon oxynitride (carbide oxidenitride) of silicon is suitable.

Moreover, in this invention, the light-semitransmissive film 2 may beapplied to any one of a single-layer structure, or a laminated structureformed of a low-transmittance layer and a high-transmittance layer.

It is desired that a preferred film thickness of thelight-semitransmissive film 2 be appropriately adjusted in view of aphase shift function and light transmittance, in particular, dependingon the material. In general, the film thickness is in a range ofpreferably 100 nm or less, and more preferably 80 nm or less.

Moreover, the light shielding film 3 having the above-mentionedlaminated structure is formed of a material containing chromium.

Examples of the above-mentioned material containing chromium include,for example, Cr simple substance or Cr compounds, e.g., CrX such as CrN,CrC, CrO, CrON, CrCN, CrOC, and CrOCN, where X represents at least onekind selected from N, C, O, and the like.

A method of forming a thin film made of a laminate film, in which thelight-semitransmissive film 2, the light shielding film 3, and the hardmask film 4 are laminated in the stated order, on the transparentsubstrate 1, e.g., the mask blank 10 illustrated in FIG. 1, does notneed to be particularly limited, but a preferred example includes, amongothers, a sputter deposition method. The sputter deposition method ispreferred because a uniform film having a constant film thickness may beformed.

In the mask blank 10 according to the first embodiment of thisinvention, as described above in Configuration 1, the light shieldingfilm 3 has the laminated structure of the lower layer 31 and the upperlayer 33, and at least contains chromium. The light shielding film 3 hasthe features that the upper layer 33 has a content of chromium of 65 at% or more, and a content of oxygen of less than 20 at %, and that thelower layer 31 has a content of chromium of less than 60 at %, and acontent of oxygen of 20 at % or more.

As described above, the upper layer 33 of the light shielding film 3containing chromium, which is immediately below the hard mask film 4,has the content of chromium of 65 at % or more, and the content ofoxygen of less than 20 at %. In other words, the upper layer 33 has ahigh content of chromium (is chromium-rich) and a low content of oxygen.As a result, the upper layer 33 is dry-etched using the mixture gas ofthe chlorine gas and the oxygen gas at a low etching rate (hereinaftersometimes simply referred to as “etching rate” for convenience of thedescription, but means the etching rate of the dry etching using themixture gas of the chlorine gas and the oxygen gas), and is hardlysusceptible to the side etching during the etching (in other words, theside walls of the pattern are hardly eroded). The upper layer 33 portionof the light shielding film 3 is hardly susceptible to the side etching,and hence the pattern shape of the hard mask film 4, which isimmediately above the upper layer 33 of the light shielding film 3, istransferred to the upper layer 33 substantially accurately. With theresist film to be formed on the surface of the mask blank 10 beingreduced in thickness, the resist pattern having the transfer pattern tobe eventually formed in the light-semitransmissive film 2 is transferredcorrectly to the hard mask film 4, and hence the pattern shape of thehard mask film 4 is transferred to the upper layer 33 substantiallyaccurately. With the light shielding film 3 including the upper layer 33having little difference from the pattern shape (for example, patterndimension) formed in the resist film, the pattern of the hard mask film4 may also be formed substantially accurately in thelight-semitransmissive film 2 containing silicon, which is patterned byanisotropic etching using the pattern of the light shielding film 3 asthe mask. In short, the pattern of the light-semitransmissive film 2 maybe formed without a divergence in dimension from the resist pattern orthe hard mask film pattern, and hence the accuracy of the pattern to beformed in the light-semitransmissive film 2 may be increased.

Meanwhile, the lower layer 31 of the light shielding film 3 has thecontent of chromium of less than 60 at %, and the content of oxygen of20 at % or more as described above. In other words, the lower layer 31has the content of chromium that is lower than that of the upper layer33, and has the content of oxygen that is higher than that of the upperlayer 33. Therefore, there is adopted the film design in which the lowerlayer 31 of the light shielding film 3 has the etching rate that ishigher than that of the upper layer 33, and hence the etching rate ofthe light shielding film 3 as a whole may be increased. It is preferredthat the lower layer 31 have a film thickness of from 70% to 97% of thetotal film thickness of the light shielding film 3. When the filmthickness of the lower layer 31 is too thin, the effect of increasingthe etching rate of the entire light shielding film 3 is reduced. Whenthe film thickness is too thick, there is a fear that the lower layer 31is side-etched too deeply.

The lower layer 31 may have a graded composition with different contentsof chromium and oxygen in a film thickness direction thereof.

As described above, in the mask blank 10 of this embodiment, the lightshielding film 3 is provided for the purpose of transferring the patternof the hard mask film 4 to the light-semitransmissive film 2 as closelyas possible. In the transfer mask, that is, the phase shift type maskmanufactured using the mask blank 10, the final transfer pattern is thepattern formed in the light-semitransmissive film 2, and the patternformed in the light shielding film 3 does not function as the transferpattern, and hence the cross-sectional shape of the light shielding filmpattern itself is not quite important. In the cross-sectional shape ofthe pattern of the light shielding film 3, even when there is someerosion in the side walls due to the side etching in the lower layer 31portion, as described above, the light shielding film 3 having theabove-mentioned laminated structure according to this invention maytransfer the pattern of the hard mask film 4 to thelight-semitransmissive film 2 as closely as possible, and hence there isno problem in the cross-sectional shape of the light shielding film 3.

According to this embodiment, even the fine transfer pattern having thepattern dimension of less than 80 nm may be formed in thelight-semitransmissive film as the transfer mask film with highaccuracy, and as a result, the transfer mask with excellent patternaccuracy may be manufactured.

In the light shielding film 3, it is preferred that the lower layer 31have a content of chromium of 40 at % or more (invention inConfiguration 2).

According to Configuration 1, the content of chromium in the lower layer31 of the light shielding film 3 is less than 60 at %. However, when thecontent of chromium is too low in the lower layer 31, the extinctioncoefficient k with respect to, for example, the ArF excimer laser light(wavelength: 193 nm) is low, and hence there arises a need to increasethe film thickness of the light shielding film 3 (especially the lowerlayer 31) to obtain the predetermined optical density. To address thisproblem, the content of chromium in the lower layer 31 is set to 40 at %or more such that the above-mentioned extinction coefficient k isincreased. Consequently, the entire light shielding film 3 may bereduced in thickness, and as a result, accuracy of patterning thelight-semitransmissive film 2 using the pattern of the light shieldingfilm 3 as a mask may be increased.

From the above description, the lower layer 31 of the light shieldingfilm 3 has the content of chromium of preferably 40 at % or more andless than 60 at %, and particularly preferably 45 at % or more and lessthan 57 at %.

Moreover, in the light shielding film 3, it is preferred that the lowerlayer 31 have a content of oxygen of 30 at % or less (invention inConfiguration 3).

According to Configuration 1, the lower layer 31 of the light shieldingfilm 3 has the content of oxygen of 20 at % or more. When the content ofoxygen in the lower layer 31 is too high, the etching rate becomes muchhigher, and there arises a problem in that a step is formed at aboundary between the upper layer 33 and the lower layer 31 in the sidewalls of the pattern. Therefore, it is preferred that the lower layer 31have the content of oxygen of 30 at % or less. When the lower layer 31has the content of oxygen in the above-mentioned range, the etching rateof the lower layer 31 becomes even higher, and hence the etching rate ofthe entire light shielding film 3 may be kept high. Moreover, when thecontent of oxygen contained in the lower layer 31 is in theabove-mentioned range, the lower layer 31 has a relatively large numberof dangling bond sites (holes) of chromium, and hence the dangling sitesof chromium and oxygen in the light-semitransmissive film 2 areconnected by chemical bonds. As a result, there may also be obtained theeffect of increasing adhesion between the light shielding film patternand the light-semitransmissive film 2. In this manner, when the adhesionbetween the light shielding film pattern and the light-semitransmissivefilm 2 is good, even when a fine pattern having a pattern dimension ofless than, for example, 80 nm is to be formed, the falling of the lightshielding film pattern may be suppressed more effectively.

From the above description, it is preferred that the lower layer 31 ofthe light shielding film 3 have the content of oxygen of 20 at % or moreand less than 30 at %.

Moreover, in the mask blank 10 according to the first embodiment, asdescribed above, the light shielding film 3 has the film configurationin which the light shielding film 3 is dry-etched using the mixture gasof the chlorine gas and the oxygen gas at the low etching rate for theupper layer 33 and the high etching rate for the lower layer 31. In thiscase, it is preferred that the etching rate of the lower layer 31 bethree times the etching rate of the upper layer 33 or more (invention inConfiguration 4).

In this manner, with the etching rate of the lower layer 31 being threetimes the etching rate of the upper layer 33 or more, the etching ratein the depth direction is increased when the etching proceeds from theupper layer 33 to the lower layer 31, and the etching in the depthdirection of the lower layer 31 may be completed while suppressing theprogress of the side etching in the upper layer 33 in a preferredmanner.

A method of adjusting the etching rates of the respective layers of thelight shielding film 3 is not particularly limited, but in thisinvention, it is preferred to adjust the etching rates by varying thecompositions of the respective layers forming the light shielding film3. Basically, the etching rates may be adjusted by adjusting thecontents of chromium or the contents of oxygen in the respective layers,but the etching rates of the respective layers may be adjusted byadjusting amount of additive of elements (for example, tin, indium, andmolybdenum) capable of increasing the etching rates. Among others, tinis particularly preferred because of having little effect on opticalcharacteristics of a film made of a chromium-based material, and furtherof being capable of increasing the etching rate in a small amount.

When tin is to be added to the light shielding film 3, tin may be addedat least in the lower layer 31 to reduce the time for over etchingduring the etching of the light shielding film 3, with the result that adisappearance of the hard mask film may be suppressed more effectively.In addition, the time during which the side walls of the upper layer 33are exposed to the etching gas may be reduced, and hence thinning of thepattern dimensions by the side etching of the upper layer 33 may also besuppressed, with the result that the light shielding film pattern havingthe excellent dimensional accuracy may be formed.

Moreover, when tin is added also to the upper layer 33, the timerequired for the etching may be further reduced. However, when tin isexcessively added, the progress of the side etching of the upper layer33 also becomes faster, and hence this is not preferred. When tin is tobe added to the upper layer 33, tin may be added so that a proportion oftin to the sum total number of chromium and tin atoms is larger in thelower layer 31 to effectively suppress the side etching in the upperlayer and to reduce the etching time required to form the lightshielding film pattern.

When a thin film to which tin is added is to be formed in the lightshielding film 3, it is preferred that the proportion of tin to the sumtotal number of chromium and tin atoms be 0.55 or less. When theproportion of tin exceeds 0.55, there is a fear that the opticalcharacteristics of the light shielding film may deviate from a desiredvalue. In addition, a proportion of tin oxide in the film is increasedto deteriorate reactivity with an etching gas (specifically,chlorine-based etching gas) for etching the chromium-based thin film,with the result that there is a possibility that the etching rate may bereduced to the contrary. A more preferred proportion of theabove-mentioned tin is 0.3 or less.

Meanwhile, even a small amount of additive of tin exerts an appropriateeffect, but a clear effect is observed at a proportion of theabove-mentioned tin of 0.01 or more, and preferably 0.1 or more.

In this invention, the lower layer of the light shielding film may havethe structure in which the bottom layer and the intermediate layer arelaminated in the stated order from the light-semitransmissive film side(invention in Configuration 5). In other words, the light shielding filmhas the laminated structure of the bottom layer, the intermediate layer,and the upper layer.

FIG. 2 is a schematic cross-sectional view for illustrating such maskblank according to a second embodiment of this invention.

As illustrated in FIG. 2, a mask blank 20 according to the secondembodiment of this invention has the structure in which, similarly tothe first embodiment described above, a light-semitransmissive film 2, alight shielding film 3, and a hard mask film 4 are laminated in thestated order on a transparent substrate 1. The light shielding film 3has the laminated structure of a bottom layer 31, an intermediate layer32, and an upper layer 33.

As in the second embodiment, with the lower layer having the structurein which the bottom layer 31 and the intermediate layer 32 are laminatedin the stated order from the light-semitransmissive film 2 side, theintermediate layer 32 is formed between the upper layer 33 and thebottom layer 31 of the light shielding film 3 so that the lightshielding film has the three-layer structure. As a result, for example,contents of chromium in the respective layers may be adjusted to controlthe etching rate of the light shielding film in three stages. Forexample, when the content of chromium in the intermediate layer 32 isadjusted to be between the contents of chromium of the upper layer 33and the bottom layer 31, that is, when the intermediate layer 32 has thecontent of chromium that is lower than that of the upper layer 33 andhigher than that of the bottom layer 31, formation of a step due to adifference in degree of progress of side etching in side walls of apattern of the light shielding film 3 may be suppressed. Consequently, across-sectional shape of the pattern may be further improved as comparedto the light shielding film having such two-layer structure as in thefirst embodiment.

In the above-mentioned second embodiment, it is preferred that theetching rate of the bottom layer 31 be three times the etching rate ofthe upper layer 33 or more (invention of Configuration 6).

In the light shielding film 3 having the three-layer structure, with theetching rate of the bottom layer 31 being three times the etching rateof the upper layer 33 or more, the side wall portion of the pattern inthe upper layer 33 is hardly etched during the etching of the bottomlayer 31. Thus, the etching in a depth direction of the bottom layer 31may be completed while suppressing the progress of the side etching inthe upper layer 33.

Further, in the above-mentioned second embodiment, it is preferred thatthe etching rate of the bottom layer 31 be higher than and two times theetching rate of the intermediate layer 32 or less (invention ofConfiguration 7).

For example, in a case where an etching rate in the bottom layer 31 isrelatively higher than that in the intermediate layer 32, when theetching proceeds from the intermediate layer 32 to the bottom layer 31,the etching rate in the depth direction is increased, but with theetching rate of the bottom layer 31 being two times the etching rate ofthe intermediate layer 32 or less as in the above-mentionedconfiguration, the etching in the bottom layer 31 and necessary overetching are completed during the etching of the bottom layer 31 beforethe side etching proceeds more in the intermediate layer 32, and henceformation of a step may be suppressed especially at the interface of theside walls of the pattern between the intermediate layer 32 and thebottom layer 31.

Moreover, it is preferred that the etching rate of the bottom layer 31be high because the time for over etching may be reduced. Meanwhile,when the etching rate of the bottom layer 31 is too high, the side wallportion of the pattern in the bottom layer portion is deeply eroded byan etching gas, and there is a risk of reducing a contact area betweenthe light-semitransmissive film and the light shielding film pattern.When the etching rate of the bottom layer 31 is in the above-mentionedrange, the erosion of the side walls of the pattern in the bottom layer31 may also be suppressed while reducing the time for over etching.

A method of adjusting the etching rates of the respective layers of thelight shielding film having the three-layer structure is similar to thatin the case of the light shielding film having the two-layer structuredescribed above.

Moreover, in the first and second embodiments described above, it ispreferred that the upper layer 33 of the light shielding film 3 have athickness of 1.5 nm or more and 8 nm or less (invention in Configuration8).

When the thickness of the upper layer 33 falls below 1.5 nm, there is anincreased risk of the erosion of the side walls of the pattern in theupper layer 33 during the dry etching. Moreover, when the thickness ofthe upper layer 33 exceeds 8 nm, there arises a fear that etching timefor the upper layer 33 may be increased. Therefore, with the upper layer33 of the light shielding film 3 having the thickness in theabove-mentioned range of 1.5 nm or more and 8 nm or less, the goodpatterning accuracy in the upper layer 33 may be maintained whilesatisfactorily suppressing the etching time of the upper layer 33. Apreferred thickness of the upper layer 33 is 3 nm or more and 8 nm orless.

When the light shielding film 3 has the three-layer structure, it ispreferred that the upper layer 33 have a thickness of 1.5 nm or more and8 nm or less as described above. Moreover, the intermediate layer 32 hasa film thickness of preferably 3 nm or more and 50 nm or less, andparticularly preferably in a range of 3 nm or more and 40 nm or less.The bottom layer 31 has a film thickness of preferably 10 nm or more and50 nm or less, and particularly preferably in a range of 20 nm or moreand 40 nm or less. With such configuration of the film thicknesses, thestep in the side walls of the pattern may be suppressed. In addition,the time required for the over etching may be reduced, and a degradationin dimensional accuracy regarding the side etching of the chromium-basedlight shielding film may be suppressed.

Moreover, in the first and second embodiments described above, it ispreferred that the light shielding film 3 have a total thickness of 35nm or more and 55 nm or less (invention in Configuration 9).

With the light shielding film 3 having the thickness of 35 nm or moreand 55 nm or less, the thickness of the entire light shielding film 3may be reduced, and the accuracy of patterning thelight-semitransmissive film 2 using the pattern of the light shieldingfilm 3 as the mask may be increased.

Moreover, in the first and second embodiments described above, the hardmask film 4 at least contains any one or both of silicon and tantalum,but is preferably formed of a material containing oxygen in addition tosilicon and tantalum, in particular (invention of Configuration 10).

The hard mask film 4 needs to be made of a material having high etchingselectivity with respect to the light shielding film 3, which isimmediately below the hard mask film 4. In particular, a materialcontaining oxygen in addition to silicon or tantalum may be selected forthe hard mask film 4 to secure the high etching selectivity with respectto the light shielding film 3, which is made of the chromium-basedmaterial, and hence not only the resist film but also the hard mask film4 may be reduced in thickness. Therefore, accuracy of transferring theresist pattern, which includes the transfer pattern formed on the frontsurface of the mask blank, to the hard mask film 4 is improved.

Specific examples of the material for forming such hard mask film 4include silicon oxide (SiO₂), silicon oxynitride (SiON), tantalum oxide(TaO), tantalum oxynitride (TaON), tantalum borate (TaBO), and tantalumboron oxynitride (TaBON).

The hard mask film 4 formed of the material containing silicon andoxygen tends to be low in adhesion with the resist film made of theorganic-based material, and hence it is preferred to performhexamethyldisilazane (HMDS) processing on a surface of the hard maskfilm 4 to improve the adhesion of the surface.

Moreover, in the first and second embodiments described above, thelight-semitransmissive film 2 at least contains silicon, but ispreferably formed of a material containing silicon and nitrogen, inparticular (invention of Configuration 11).

With the material containing silicon and nitrogen being applied to thelight-semitransmissive film 2, the etching selectivity with respect tothe chromium-based light shielding film 3 may be secured. Alternatively,when the material containing silicon and nitrogen is used, thepatterning using the anisotropic fluorine-based gas as the etching gasmay be applied. Therefore, the transfer pattern having the excellentpattern accuracy may also be formed in the light-semitransmissive film 2by the anisotropic etching using as the mask the pattern of the lightshielding film 3, to which the pattern shape of the hard mask film 4 hasbeen transferred substantially accurately.

Further, it is preferred that, in the first and second embodimentsdescribed above, the light-semitransmissive film 2 and the lightshielding film 3 form a laminated structure having a transmittance of0.2% or less with respect to an ArF excimer laser light (wavelength: 193nm) (invention of Configuration 12).

As described above, the laminated structure of thelight-semitransmissive film 2 and the light shielding film 3 has atransmittance of 0.2% or less with respect to the ArF excimer laserlight (wavelength: 193 nm). Thus, the laminated structure has good lightshielding property (optical density of 2.7 or more) with respect to theArF excimer laser light as the exposure light, which is required of thelight shielding band, for example, in a preferred manner.

Further, it is preferred that, in the first and second embodimentsdescribed above, the light-semitransmissive film 2 and the lightshielding film 3 form a laminated structure having a transmittance of50% or less with respect to light having a wavelength in at least a partof a wavelength region of from 800 nm to 900 nm (invention ofConfiguration 13).

The resist is not sensitive to light in a near-infrared region having awavelength of from 800 nm to 900 nm, and hence the light is used foralignment when the mask blank is placed in an exposure apparatus. As inthis configuration, the laminated structure of thelight-semitransmissive film 2 and the light shielding film 3 has atransmittance of 50% or less with respect to light having a wavelengthin at least a part of the wavelength region of from 800 nm to 900 nm.Thus, the laminated structure enables easy placement of the mask blankin the exposure apparatus in a preferred manner.

Moreover, in the first and second embodiments described above, both ofthe hard mask film 4 and light-semitransmissive film 2 may be patternedby the dry etching using the fluorine-based gas (invention ofConfiguration 14). Consequently, together with the substantiallyaccurate transfer of the pattern shape of the hard mask film 4, which isimmediately above the upper layer 33 of the light shielding film 3, tothe upper layer 33, the transfer pattern having the excellent formaccuracy of the pattern may be formed in the light-semitransmissive film2 by the patterning by means of the anisotropic etching using the lightshielding film 3 as the mask.

This invention also provides a method of manufacturing a transfer maskusing the above-mentioned mask blank according to this invention(invention of Configuration 15).

FIG. 3A to FIG. 3E are schematic cross-sectional views of the mask blankand the like, for illustrating manufacturing steps of the transfer maskusing the mask blank 10 according to the first embodiment of thisinvention or the mask blank 20 according to the second embodiment ofthis invention. FIG. 3A to FIG. 3E are intended to enhance theunderstanding of the manufacturing steps, and cross-sectional shapes ofthe patterns illustrated in FIG. 3A to FIG. 3E do not correctlyrepresent cross-sectional shapes that are actually formed.

First, for example, a predetermined resist pattern 5 is formed on thesurface of the mask blank 10 (see FIG. 3A). This resist pattern 5 has adesired pattern, which is the final transfer pattern to be formed in thelight-semitransmissive film 2. When the mask blank 20 is used, themanufacturing steps are the same.

Next, a hard mask film pattern 4 a corresponding to the pattern of thelight-semitransmissive film is formed in the hard mask film 4 by the dryetching using the fluorine-based gas, and using as a mask the resistpattern 5, which is formed on the hard mask film 4 of the mask blank 10and has the above-mentioned light-semitransmissive film pattern (seeFIG. 3B).

Next, a light shielding film pattern 3 a corresponding to thelight-semitransmissive film pattern is formed in the light shieldingfilm 3 having the laminate structure by the dry etching using themixture gas of the chlorine gas and the oxygen gas, and using as a maskthe hard mask film pattern 4 a formed as described above (see FIG. 3C).

Next, a light-semitransmissive film pattern 2 a is formed in thelight-semitransmissive film 2 by the dry etching using thefluorine-based gas, and using as a mask the light shielding film pattern3 a formed as described above (see FIG. 3D). In the etching step of thelight-semitransmissive film 2, the hard mask film pattern 4 a that isexposed on the surface is removed.

Next, a resist film is applied on the entire surface of the lightshielding film pattern 3 a, and a resist pattern (not illustrated),which corresponds to the light shielding pattern (for example, lightshielding band pattern) to be formed in the light shielding film, isformed through predetermined exposure and development processing. Then,a predetermined light shielding pattern 3 b is formed in thelight-semitransmissive film pattern 2 a by the dry etching using themixture gas of the chlorine gas and the oxygen gas, and using the resistpattern as a mask. Finally, the remaining resist pattern is removed tocomplete a transfer mask (for example, halftone-type phase shift mask)30 (see FIG. 3E).

As is apparent from the above description, the transfer mask may bemanufactured following the above-mentioned manufacturing steps using themask blank 10 according to the first embodiment of this invention or themask blank 20 according to the second embodiment of this invention toobtain the transfer mask in which even the fine transfer pattern isformed with high pattern accuracy. More specifically, according to themask blank 10 or the mask blank 20 of the embodiments of this invention,the upper layer 33 of the light shielding film 3 has the high content ofchromium (is chromium-rich) and the low content of oxygen, and hence hasthe low etching rate, with the result that the pattern of the upperlayer 33 is less susceptible to the side etching. Therefore, there canbe formed the pattern of the light shielding film 3 including the upperlayer 33 to which the shape of the transfer pattern, which is formed inthe resist film or the hard mask film 4, is transferred substantiallyaccurately. As a result, when the light-semitransmissive film 2 ispatterned using the light shielding film pattern as the mask, thetransfer pattern having the excellent pattern accuracy may also beformed in the light-semitransmissive film 2.

As described above, even when a fine pattern is formed, there is no suchproblem as the falling of the light shielding film pattern, and thepattern of the light-semitransmissive film 2 may also be formed withhigh pattern accuracy. As a result, there may be obtained a transfermask in which the fine pattern is formed with the high pattern accuracy.

Moreover, according to a method of manufacturing a semiconductor device,which includes a step of patterning and transferring the transferpattern of the transfer mask to the semiconductor substrate by alithography method using the transfer mask which has been manufacturedby the above-mentioned method of manufacturing the transfer maskaccording to this invention and in which the above-mentioned finepattern is formed with the high pattern accuracy, a high-qualitysemiconductor device with excellent pattern accuracy may be obtained.

EXAMPLE

Now, the present invention will be described in more detail by way ofExamples.

Example 1

Example 1 according to this invention relates to a mask blank for use inmanufacturing of a halftone-type phase shift mask using the ArF excimerlaser having the wavelength of 193 nm as the exposure light, andcorresponds to the first embodiment described above.

The mask blank used in this Example has the structure in which thelight-semitransmissive film 2, the light shielding film 3 having thetwo-layer laminated structure, and the hard mask film 4 are laminated inthe stated order on the transparent substrate (glass substrate) 1 asillustrated in FIG. 1. This mask blank was manufactured as follows.

As the glass substrate, a synthetic quartz substrate (having a size ofabout 152 mm by about 152 mm and a thickness of 6.35 mm) was prepared.

Then, the above-mentioned synthetic quartz substrate was placed in asheet-type DC sputtering apparatus, and a MoSiN light-semitransmissivefilm (phase shift film) made of molybdenum, silicon, and nitrogen wasformed to have a thickness of 69 nm on the synthetic quartz substrate byreactive sputtering (DC sputtering) using a mixed sintered target ofmolybdenum (Mo) and silicon (Si) (Mo:Si=12 at %:88 at %), and using as asputtering gas a mixture gas of argon (Ar), nitrogen (N₂), and helium(He) (at a ratio of flow rates of ArN₂:He=8:72:100 and a pressure of 0.2Pa). A composition of the formed MoSiN film was Mo:Si:N=4.1:35.6:60.3(at % ratio). The composition was measured by XPS.

Next, the substrate was taken out of the sputtering apparatus, andheating processing in the air was performed on thelight-semitransmissive film on the above-mentioned synthetic quartzsubstrate. This heating processing was performed at 450° C. for 30minutes. On the light-semitransmissive film after this heatingprocessing, when a transmittance and a phase shift amount at thewavelength (193 nm) of the ArF excimer laser were measured using a phaseshift amount measurement apparatus, the transmittance was 6.44%, and thephase shift amount was 174.3 degrees.

Next, the substrate on which the above-mentioned light-semitransmissivefilm had been formed was put in the sputtering apparatus again, and alight shielding film having a laminated structure of a lower layer madeof a CrOCN film and an upper layer made of a CrN film was formed on theabove-mentioned light-semitransmissive film. Specifically, reactivesputtering was performed in a mixture gas atmosphere of argon (Ar),carbon dioxide (CO₂), nitrogen (N₂), and helium (He) (at a ratio of flowrates of Ar:CO₂:N₂:He=20:24:22:30 and a pressure of 0.3 Pa) using atarget made of chromium so that the lower layer of the light shieldingfilm made of the CrOCN film was formed to have a thickness of 47 nm onthe above-mentioned light-semitransmissive film. Subsequently, reactivesputtering was performed in a mixture gas atmosphere of argon (Ar) andnitrogen (N₂) (at a ratio of flow rates of Ar:N₂=25:5 and a pressure of0.3 Pa) similarly using the target made of chromium so that the upperlayer of the light shielding film made of the CrN film was formed tohave a thickness of 5 nm on the above-mentioned lower layer.

A composition of the formed CrOCN film as the lower layer of the lightshielding film was Cr:O:C:N=49.2:23.8:13.0:14.0 (at % ratio) and acomposition of the CrN film as the upper layer of the light shieldingfilm was Cr:N=76.2:23.8 (at % ratio). Those compositions were measuredby XPS.

Next, a hard mask film made of a SiON film was formed on theabove-mentioned light shielding film. Specifically, reactive sputteringwas performed in a mixture gas atmosphere of argon (Ar), nitrogenmonoxide (NO), and helium (He) (at a ratio of flow rates ofAr:NO:He=8:29:32 and a pressure of 0.3 Pa) using a target of silicon sothat the hard mask film made of the SiON film was formed to have athickness of 15 nm on the above-mentioned light shielding film. Acomposition of the formed SiON film was Si:O:N=37:44:19 (at % ratio).The composition was measured by XPS.

An optical density of the above-mentioned laminated structure of thelight-semitransmissive film and the light shielding film was 3.0 or more(transmittance of 0.1% or less) at the wavelength (193 nm) of the ArFexcimer laser. Moreover, a transmittance at a wavelength of 880 nm(wavelength used for alignment of the substrate to be loaded in anexposure apparatus) was 50% or less.

The mask blank according to this Example was manufactured as describedabove.

Next, a halftone-type phase shift mask was manufactured using the maskblank and following the above-mentioned manufacturing steps illustratedin FIG. 3. Reference numerals in the following description correspond tothe reference numerals in FIG. 1 and FIG. 3.

First, HMDS processing was performed on an upper surface of the maskblank 10. A chemical amplification resist for electron beam lithography(PRL 009 manufactured by FUJIFILM Electronic Materials Co., Ltd.) wasapplied by spin coating, and predetermined baking processing wasperformed so that a resist film was formed to have a film thickness of150 nm.

Next, a predetermined device pattern (pattern corresponding to a phaseshift pattern to be formed in the light-semitransmissive film 2 (phaseshift layer) and including lines and spaces) was drawn on theabove-mentioned resist film using an electron beam lithographyapparatus. Then, the resist film was developed to form a resist pattern5 (see FIG. 3A).

Next, the hard mask film 4 was dry-etched using the resist pattern 5 asthe mask to form the hard mask film pattern 4 a (see FIG. 3B). Afluorine-based gas (SF₆) was used as a dry etching gas.

After removing the resist pattern 5, the light shielding film 3 made ofthe laminated film of the upper layer and the lower layer was dry-etchedsuccessively using the hard mask film pattern 4 a as a mask to form thelight shielding film pattern 3 a (see FIG. 3C). A mixture gas of Cl₂ andO₂ (Cl₂:O₂=8:1 (ratio of flow rates)) was used as a dry etching gas. Theetching rate of the light shielding film 3 was 2.9 Å/sec for the upperlayer and 5.1 Å/sec for the lower layer.

Subsequently, the light-semitransmissive film 2 was dry-etched using thelight shielding film pattern 3 a as a mask to form thelight-semitransmissive film pattern 2 a (phase shift film pattern) (seeFIG. 3D). A fluorine-based gas (SF₆) was used as a dry etching gas. Inthe etching step of the light-semitransmissive film 2, the hard maskfilm pattern 4 a that is exposed on the surface was removed.

Next, the above-mentioned resist film was formed again on the entiresurface of the substrate in the above-mentioned state of FIG. 3D by spincoating. A predetermined device pattern (for example, patterncorresponding to light shielding band pattern) was drawn using theelectron beam lithography apparatus, and was then developed to form thepredetermined resist pattern. Subsequently, the exposed light shieldingfilm pattern 3 a was etched using the resist pattern as a mask toremove, for example, the light shielding film pattern 3 a in a transferpattern forming region, and a light shielding band pattern 3 b wasformed in a peripheral portion of the transfer pattern forming region. Amixture gas of Cl₂ and O₂ (Cl₂:O₂=8:1 (ratio of flow rates)) was used asa dry etching gas in this case.

Finally, the remaining resist pattern was removed to manufacture thehalftone-type phase shift mask 30 (see FIG. 3E).

[Evaluation of Light Shielding Film Pattern]

When a cross-sectional shape of the light shielding film pattern waschecked after the above-mentioned step of etching thelight-semitransmissive film 2 (step in FIG. 3D) was ended, thecross-sectional shape as illustrated in FIG. 4 was observed. Morespecifically, although the side walls of the upper layer of the lightshielding film is slightly eroded from the pattern of the hard maskfilm, the form defined by the hard mask film pattern may be obtained,and the hard mask film pattern was transferred accurately. The hard maskfilm pattern 4 a had been removed at this point in time, and hence thestate before the removal is illustrated by the broken line in FIG. 4.

Moreover, as a result of reducing a line width of a line-and-spacepattern, which was formed in the above-mentioned resist film, in stepsof 10 nm from 200 nm, and checking a formed state of the light shieldingfilm pattern, the pattern was able to be formed up to a 50 nm width.

[Evaluation of Light-Semitransmissive Film Pattern]

When the light-semitransmissive film pattern, which was formed by thedry etching using the above-mentioned light shielding film pattern asthe mask, was evaluated, as apparent from FIG. 4, the shape defined bythe pattern of the upper layer of the light shielding film was able tobe obtained, and the light-semitransmissive film pattern with anexcellent CD characteristic was able to be formed. In other words, evenwith the fine pattern, the transfer pattern was able to be formed withexcellent pattern accuracy and a small divergence from the hard maskfilm pattern.

Example 2

Example 2 according to this invention relates to a mask blank for use inmanufacturing of a halftone-type phase shift mask using the ArF excimerlaser having the wavelength of 193 nm as the exposure light, andcorresponds to the second embodiment described above.

The mask blank used in this Example has the structure in which thelight-semitransmissive film 2, the light shielding film 3 having thethree-layer laminated structure, and the hard mask film 4 are laminatedin the stated order on the transparent substrate (glass substrate) 1 asillustrated in FIG. 2. This mask blank was manufactured as follows.

As the glass substrate, a synthetic quartz substrate (having a size ofabout 152 mm by about 152 mm and a thickness of 6.35 mm) was prepared.

Then, the above-mentioned synthetic quartz substrate was placed in asheet-type DC sputtering apparatus, and a MoSiN light-semitransmissivefilm (phase shift film) made of molybdenum, silicon, and nitrogen wasformed to have a thickness of 69 nm on the synthetic quartz substrate byreactive sputtering (DC sputtering) using a mixed sintered target ofmolybdenum (Mo) and silicon (Si) (Mo:Si=12 at %:88 at %), and using as asputtering gas a mixture gas of argon (Ar), nitrogen (N₂), and helium(He) (at a ratio of flow rates of ArN₂:He=8:72:100 and a pressure of 0.2Pa). A composition of the formed MoSiN film was Mo:Si:N=4.1:35.6:60.3(at % ratio). The composition was measured by XPS.

Next, the substrate was taken out of the sputtering apparatus, andheating processing in the air was performed on thelight-semitransmissive film on the above-mentioned synthetic quartzsubstrate. This heating processing was performed at 450° C. for 30minutes. On the light-semitransmissive film after this heatingprocessing, when a transmittance and a phase shift amount at thewavelength (193 nm) of the ArF excimer laser were measured using a phaseshift amount measurement apparatus, the transmittance was 6.44%, and thephase shift amount was 174.3 degrees.

Next, the substrate on which the above-mentioned light-semitransmissivefilm had been formed was put in the sputtering apparatus again, and alight shielding film having a laminated structure of a lower layer(bottom layer) made of a CrOCN film, an intermediate layer made of aCrOCN film, and an upper layer made of a CrN film was formed on theabove-mentioned light-semitransmissive film. Specifically, reactivesputtering was performed in a mixture gas atmosphere of argon (Ar),carbon dioxide (CO₂), nitrogen (N₂), and helium (He) (at a ratio of flowrates of Ar:CO₂:N₂:He=20:24:22:30 and a pressure of 0.3 Pa) using atarget made of chromium so that the lower layer of the light shieldingfilm made of the CrOCN film was formed to have a thickness of 15 nm onthe above-mentioned light-semitransmissive film. Subsequently, reactivesputtering was performed in a mixture gas atmosphere of argon (Ar),carbon dioxide (CO₂), nitrogen (N₂), and helium (He) (at a ratio of flowrates of Ar:CO₂:N₂:He=20:25:13:30 and a pressure of 0.3 Pa) similarlyusing the target made of chromium so that the intermediate layer of thelight shielding film made of the CrOCN film was formed to have athickness of 27 nm on the above-mentioned lower layer. Then reactivesputtering was performed in a mixture gas atmosphere of argon (Ar) andnitrogen (N₂) (at a ratio of flow rates of Ar:N₂=25:5 and a pressure of0.3 Pa) similarly using the target made of chromium so that the upperlayer of the light shielding film made of the CrN film was formed tohave a thickness of 3.7 nm on the above-mentioned intermediate layer.

A composition of the formed CrOCN film as the lower layer of the lightshielding film was Cr:O:C:N=49.2:23.8:13.0:14.0 (at % ratio). Moreover,a composition of the CrOCN film as the intermediate layer of the lightshielding film was Cr:O:C:N=55.2:22:11.6:11.1 (at % ratio), and acomposition of the CrN film as the upper layer of the light shieldingfilm was Cr:N=76.2:23.8 (at % ratio). Those compositions were measuredby XPS.

Next, a hard mask film made of a SiON film was formed on theabove-mentioned light shielding film. Specifically, reactive sputteringwas performed in a mixture gas atmosphere of argon (Ar), nitrogenmonoxide (NO), and helium (He) (at a ratio of flow rates ofAr:NO:He=8:29:32 and a pressure of 0.3 Pa) using a target of silicon sothat the hard mask film made of the SiON film was formed to have athickness of 15 nm on the above-mentioned light shielding film. Acomposition of the formed SiON film was Si:O:N=37:44:19 (at % ratio).The composition was measured by XPS.

An optical density of the above-mentioned laminate structure of thelight-semitransmissive film and the light shielding film was 3.0 or more(transmittance of 0.1% or less) at the wavelength (193 nm) of the ArFexcimer laser. Moreover, a transmittance at a wavelength of 880 nm(wavelength used for alignment of the substrate to be loaded in anexposure apparatus) was 50% or less.

The mask blank 20 according to this Example was manufactured asdescribed above.

Next, a halftone-type phase shift mask was manufactured using the maskblank and following the above-mentioned manufacturing steps illustratedin FIG. 3A to FIG. 3E. Reference numerals in the following descriptioncorrespond to the reference numerals in FIG. 2 and FIG. 3A to FIG. 3E.

First, HMDS processing was performed on an upper surface of the maskblank 20. A chemical amplification resist for electron beam lithography(PRL 009 manufactured by FUJIFILM Electronic Materials Co., Ltd.) wasapplied by spin coating, and predetermined baking processing wasperformed so that a resist film was formed to have a film thickness of150 nm.

Next, a predetermined device pattern (pattern corresponding to a phaseshift pattern to be formed in the light-semitransmissive film 2 (phaseshift layer) and including lines and spaces) was drawn on theabove-mentioned resist film using an electron beam lithographyapparatus. Then, the resist film was developed to form a resist pattern5 (see FIG. 3A).

Next, the hard mask film 4 was dry-etched using the resist pattern 5 asthe mask to form the hard mask film pattern 4 a (see FIG. 3B). Afluorine-based gas (SF₆) was used as a dry etching gas.

After removing the resist pattern 5, the light shielding film 3 made ofthe laminated film of the upper layer, the intermediate layer, and thelower layer was dry-etched successively using the hard mask film pattern4 a as a mask to form the light shielding film pattern 3 a (see FIG.3C). A mixture gas of Cl₂ and O₂ (Cl₂:O₂=8:1 (ratio of flow rates)) wasused as a dry etching gas. The etching rate of the light shielding film3 was 2.9 Å/sec for the upper layer, 5.1 Å/sec for the intermediatelayer, and 9.1 Å/sec for the lower layer.

Subsequently, the light-semitransmissive film 2 was dry-etched using thelight shielding film pattern 3 a as a mask to form thelight-semitransmissive film pattern 2 a (phase shift film pattern) (seeFIG. 3D). A fluorine-based gas (SF₆) was used as a dry etching gas. Inthe etching step of the light-semitransmissive film 2, the hard maskfilm pattern 4 a that is exposed on the surface was removed.

Next, the above-mentioned resist film was formed again on the entiresurface of the substrate in the above-mentioned state of FIG. 3D by spincoating. A predetermined device pattern (for example, patterncorresponding to light shielding band pattern) was drawn using theelectron beam lithography apparatus, and was then developed to form thepredetermined resist pattern. Subsequently, the exposed light shieldingfilm pattern 3 a was etched using the resist pattern as a mask toremove, for example, the light shielding film pattern 3 a in a transferpattern forming region, and a light shielding band pattern 3 b wasformed in a peripheral portion of the transfer pattern forming region. Amixture gas of Cl₂ and O₂ (Cl₂:O₂=8:1 (ratio of flow rates)) was used asa dry etching gas in this case.

Finally, the remaining resist pattern was removed to manufacture thehalftone-type phase shift mask 20 (see FIG. 3E).

[Evaluation of Light Shielding Film Pattern]

When a cross-sectional shape of the light shielding film pattern waschecked after the above-mentioned step of etching thelight-semitransmissive film 2 (step in FIG. 3D) was ended, thecross-sectional shape as illustrated in FIG. 5 was observed. Morespecifically, although the side walls of the upper layer of the lightshielding film is slightly eroded from the pattern of the hard mask film(by an amount smaller than that in Example 1), the form defined by thehard mask film pattern was able to be obtained substantially accurately,and the hard mask film pattern was transferred accurately. This isbecause, although the etching rate of the lower layer is high, theetching rate of the intermediate layer, which is above the lower layer,is low, and as a result, the erosion of the side walls of the pattern bythe etching gas was able to be suppressed effectively. Thecross-sectional shape of the light shielding film pattern was betterthan that in Example 1. The hard mask film pattern 4 a had been removedat this point in time, and hence the state before the removal isillustrated by the broken line in FIG. 5.

Moreover, as a result of reducing a line width of a line-and-spacepattern, which was formed in the above-mentioned resist film, in stepsof 10 nm from 200 nm, and checking a formed state of the light shieldingfilm pattern, the pattern was able to be formed up to a 40 nm width.

[Evaluation of Light-Semitransmissive Film Pattern]

When the light-semitransmissive film pattern, which was formed by thedry etching using the above-mentioned light shielding film pattern asthe mask, was evaluated, as apparent from FIG. 5, the shape defined bythe pattern of the upper layer of the light shielding film was able tobe obtained, and the light-semitransmissive film pattern with anexcellent CD characteristic was able to be formed. In other words, evenwith the fine pattern, the transfer pattern was able to be formed withexcellent pattern accuracy and a small divergence from the hard maskfilm pattern.

Comparative Example

A mask blank was manufactured with the light-semitransmissive film andthe hard mask film being films similar to those in Example 1 and withthe configuration of the light shielding film being different from thatin Example 1. More specifically, the light shielding film in thisComparative Example is a light shielding film having the single-layerstructure, and is a thin film having the same composition as thecomposition of the lower layer of the light shielding film in Example 1,an optical density of 3.0 or more, and a film thickness of 100 nm.

The mask blank in this Comparative Example was used to manufacture ahalftone-type phase shift mask in a method similar to that in Example 1.

[Evaluation of Light Shielding Film Pattern]

When a cross-sectional shape of the light shielding film pattern waschecked after the above-mentioned step of patterning the light shieldingfilm 3 (step in FIG. 3C) was ended, the cross-sectional shape asillustrated in FIG. 6 was observed. More specifically, the lightshielding film had a shape that was deeply hollowed by the erosion dueto the etching in the wall surface of the pattern. Moreover, line widthswere thinner than those in the pattern of the hard mask film, and had atendency toward a large divergence in dimension from the hard mask filmpattern.

Moreover, as a result of reducing a line width of a line-and-spacepattern, which was formed in the above-mentioned resist film, in stepsof 10 nm from 200 nm, and checking a formed state of the light shieldingfilm pattern as in Example 1, the falling of the light shielding filmpattern occurred at an 80 nm width.

Therefore, even when such fine pattern as the lines and spaces of, forexample, 80 nm or less was to be formed using the mask blank in thisComparative Example, the light shielding film falls, and it is difficultto pattern the light-semitransmissive film, which functions as a finaltransfer pattern.

The embodiments and Examples of this invention have been describedabove. However, those embodiments and Examples are merely exemplary, anddo not limit the scope of claims. The technology described in the scopeof claims encompasses various alterations and modifications to thespecific examples exemplified above.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2014-070686, filed on Mar. 30, 2014, thedisclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   -   1 transparent substrate    -   2 light-semitransmissive film    -   3 light shielding film    -   31 lower layer of light shielding film (bottom layer)    -   32 intermediate layer of light shielding film    -   33 upper layer of light shielding film    -   4 hard mask film    -   5 resist pattern    -   10, 20 mask blank    -   30 transfer mask

1. A mask blank having a structure in which a light-semitransmissivefilm, and a light shielding film are laminated in the stated order on atransparent substrate, the light-semitransmissive film at leastcontaining silicon, the light shielding film consisting of a laminatedstructure of a lower layer and an upper layer, the light shielding filmcontaining at least containing chromium, the lower layer having acontent of the chromium of less than 60 at %, and a content of oxygen of20 at % or more, the upper layer having a content of the chromium of 65at % or more, and a content of oxygen of less than 20 at %, the upperlayer having a thickness of 1.5 nm or more and 8 nm or less, wherein alaminated structure of the light-semitransmissive film and the lightshielding film has a transmittance of 50% or less with respect to lighthaving a wavelength in at least a part of a wavelength region of from800 nm to 900 nm.
 2. The mask blank according to claim 1, wherein thelower layer has a content of the chromium of 40 at % or more.
 3. Themask blank according to claim 1, wherein the lower layer has a contentof the oxygen of 30 at % or less.
 4. The mask blank according to claim1, wherein the light shielding film has a thickness of 35 nm or more and55 nm or less.
 5. The mask blank according to claim 1, wherein the lowerlayer has a thickness of 70% or more and 97% or less with respect to athickness of the light shielding film.
 6. The mask blank according toclaim 1, wherein a laminated structure of the light-semitransmissivefilm and the light shielding film has a transmittance of 0.2% or lesswith respect to an ArF excimer laser light (wavelength: 193 nm).
 7. Amask blank having a structure in which a light-semitransmissive film,and a light shielding film are laminated in the stated order on atransparent substrate, the light-semitransmissive film at leastcontaining silicon, the light shielding film consisting of a laminatedstructure of a bottom layer, an intermediate layer and an upper layer,the light shielding film containing at least containing chromium, thebottom layer having a content of the chromium of less than 60 at %, anda content of oxygen of 20 at % or more, the intermediate layer having acontent of the chromium of less than 60 at %, and a content of oxygen of20 at % or more, the upper layer having a content of the chromium of 65at % or more, and a content of oxygen of less than 20 at %, the upperlayer having a thickness of 1.5 nm or more and 8 nm or less, wherein thecontent of the chromium in the intermediate layer is greater than thecontent of the chromium in the bottom layer, and wherein a laminatedstructure of the light-semitransmissive film and the light shieldingfilm has a transmittance of 50% or less with respect to light having awavelength in at least a part of a wavelength region of from 800 nm to900 nm.
 8. The mask blank according to claim 7, wherein the bottom layerhas a content of the chromium of 40 at % or more.
 9. The mask blankaccording to claim 7, wherein the intermediate layer has a content ofthe chromium of 40 at % or more.
 10. The mask blank according to claim7, wherein the bottom layer has a content of the oxygen of 30 at % orless.
 11. The mask blank according to claim 7, wherein the intermediatelayer has a content of the oxygen of 30 at % or less.
 12. The mask blankaccording to claim 7, wherein the light shielding film has a thicknessof 35 nm or more and 55 nm or less.
 13. The mask blank according toclaim 7, wherein the bottom layer has a thickness of 10 nm or more and50 nm or less.
 14. The mask blank according to claim 7, wherein theintermediate layer has a thickness of 3 nm or more and 50 nm or less.15. The mask blank according to claim 7, wherein a laminated structureof the light-semitransmissive film and the light shielding film has atransmittance of 0.2% or less with respect to an ArF excimer laser light(wavelength: 193 nm).
 16. A method of manufacturing a transfer maskusing the mask blank of claim 1, the method comprising the steps of:forming a transfer pattern, which corresponds to a final transferpattern to be formed in the light-semitransmissive film, in the lightshielding film by dry etching using a mixture gas of a chlorine gas andan oxygen gas; forming the final transfer pattern in thelight-semitransmissive film by dry etching using a fluorine-based gasand using as a mask the light shielding film, in which the transferpattern has been formed; and forming a light shielding pattern in thelight shielding film by dry etching using a mixture gas of a chlorinegas and an oxygen gas, and using as a mask a resist film, which isformed on the light shielding film and has a light shielding pattern.17. A method of manufacturing a semiconductor device, comprising a stepof patterning and transferring a transfer pattern of a transfer mask,which is manufactured by the method of manufacturing a transfer mask ofclaim 16, on a semiconductor substrate by a lithography method using thetransfer mask.
 18. A method of manufacturing a transfer mask using themask blank of claim 7, the method comprising the steps of: forming atransfer pattern, which corresponds to a final transfer pattern to beformed in the light-semitransmissive film, in the light shielding filmby dry etching using a mixture gas of a chlorine gas and an oxygen gas;forming the final transfer pattern in the light-semitransmissive film bydry etching using a fluorine-based gas and using as a mask the lightshielding film, in which the transfer pattern has been formed; andforming a light shielding pattern in the light shielding film by dryetching using a mixture gas of a chlorine gas and an oxygen gas, andusing as a mask a resist film, which is formed on the light shieldingfilm and has a light shielding pattern.
 19. A method of manufacturing asemiconductor device, comprising a step of patterning and transferring atransfer pattern of a transfer mask, which is manufactured by the methodof manufacturing a transfer mask of claim 18, on a semiconductorsubstrate by a lithography method using the transfer mask.